Patrick Connaro, a 42-year-old robotics engineer living in Colorado Springs, was sitting in the bleachers one warm Saturday afternoon in 2003, watching his son's Little League game, when the ground opened beneath him.

"My little boy was there, he was up at bat, and I started yelling for him, 'Go Matthew [not his real name]! Knock it out of the park!' And another man started screaming for Matthew. Louder than me. I looked over, and I looked at him, and I was like, Who is this guy? And I looked at my son, and I looked at him . . . and they were identical."

After the ball game, Connaro ordered a paternity test. The results came back 2 weeks later. "I opened up the letter from Labcorp, and it said, ' . . . 99.9 percent chance you are not the biological father of this child.' I started crying. My head started spinning."

Connaro admits that the possibility had crossed his mind before, given his son's dissimilar facial features, but each time he questioned his wife about it, she vehemently denied the suggestion. Even when he showed her the test results, she still denied it. "She said, 'You forged this,' " Connaro recalls, shaking his head in amazement.

To this day he remembers that game with a kind of nightmarish clarity. Matthew struck out. Connaro had planned on going over and giving him a hug, along with a few words of fatherly consolation, but when he heard the other guy yelling, he just stood up and walked away.

"I was so disillusioned, I just didn't know what to say. It was horrible. I don't think anybody could experience what I experienced there."

Some call this paternity fraud. But a more accurate term is "paternal discrepancy." Paternity fraud emphasizes the financial aspect of the phenomenon, but paternal discrepancy (PD) describes the anomaly itself--the disconnect between what men think is true and the genetic reality. And research shows that it's a lot more common than we might believe.

After recently reviewing 67 studies on the subject, University of Oklahoma researchers found that PD rates tend to be much higher among men who have reason to believe there's been more than one dog in the yard. No surprise there. But leave out these men and you end up with a number that can safely be assumed to represent the rest of us. That number is 3.85 percent. Another review of 19 studies by a group at Liverpool John Moores University backs this up, putting the figure at 3.7 percent of dads. It may not seem like a lot--until you do the math. According to a 2005 U.S. Census Bureau report, there are 27,940,000 fathers nationwide with a child under 18. That means over a million guys out there are taking care of some other man's kid.

Compared with this, infidelity by itself is a mere white lie, a misdemeanor, maybe even forgivable. But this . . . this lie unravels years of commitment in a single stroke. Does forgiveness even apply here?

There are those who believe that biology shouldn't make a difference, that fatherhood is just a social construct. Connaro himself refuses to let genetics stand between him and his son. "I'm the only man that he knows as his dad," he says. "Why should I lose that bond and that love?"

Many men in Connaro's position might not feel the same way. Studies show that evolution has designed men to care deeply about who their children are. In 2003, for instance, researchers at the State University of New York at Albany recruited 20 men and 20 women, then morphed their facial features with photographs of children. Subsequent testing showed that the women responded equally to photos of kids whose faces resembled theirs and those that resembled the faces of strangers. The men, on the other hand, reacted far more positively to children whose faces resembled their own.

"It's not reproductively beneficial to invest all your resources in a child who is not carrying on your genetic line," says study author Rebecca Burch, Ph.D. "Men throughout the history of the species who have invested all their time and energy in children who weren't theirs no longer have genes in the population."

They are, in other words, extinct.

When the stakes are this high, there is no greater deception than PD. It's a lie that reaches right down to your chromosomes, and when the truth finally comes out, the revelation can be devastating.

Seven years ago, on an otherwise idyllic summer Saturday afternoon, Tony Winbush, 34, was throwing a football with his 5-year-old son in the backyard of his home in Tallahassee, Florida, when he discovered he was not the child's father. The boy himself told Winbush.

"He said, 'My mom told me that I have two dads.' I said, 'Son, you can't have but one dad. I'm the only dad you've got.' He said, 'That's what my mama told me--I have two.' " Within a month, the family ceased to exist. "It got to a point," says Winbush, "where it bothered me so bad, I had to seek psychiatric help."

But while men may be the primary victims of PD, women aren't the only villains. Paternal discrepancy makes liars of everyone, and that includes the people from whom we'd most expect the truth.

Morgan Wise, a 44-year-old train engineer from Big Spring, Texas, might have remained ignorant forever if his fourth child hadn't been diagnosed with cystic fibrosis (CF). Presumed to be a carrier of the CF gene, Wise had his own DNA tested to identify which of the many gene mutations of the disease the boy had inherited. (There are more than 1,000.) The test revealed that Wise was not a carrier, which could only mean one thing: This was not his child.

"I nearly fell out of my chair," Wise says, recalling his doctor giving him the news. "I said, 'What are you getting at?' And he told me, 'Morgan, you're not the first, and you won't be the last.' "

Men rely on their doctors to level with them when things are dire. The steady stare, the hand on the shoulder . . . breaking bad news is their business. And yet, Wise's doctor is actually the exception to the rule. The fact is, the overwhelming majority of physicians will not tell a man the truth about PD.

"Most doctors are going to say to themselves, Jeez, I don't want to cause a problem in this family by disclosing this information that I just stumbled across," says Alan Meisel, J.D., director of the Center for Bioethics and Health Law at the University of Pittsburgh. "Why create problems if I don't have to?"

Being lied to once is bad enough, but this second betrayal can bring a man to his knees. If you can't trust your doctor, whom can you trust?

"If the father asked me point-blank, 'Is this my son, my biological son? Can you tell by the tests?' I would have to tell him the truth," says Mikel Prieto, M.D., a kidney-transplant surgeon at the Mayo Clinic in Rochester, Minnesota. "Would I volunteer that information if it did not come up in the conversation, and did not affect what we were going to do? Probably I wouldn't."

Just 6 months after making this statement, Dr. Prieto said he had changed his mind. "Now, as a general rule, our group favors full disclosure of paternity issues."

Genuine or not, it's an ethical 180 that more doctors need to make, especially when you factor in the potential medical consequences of staying silent. If a child is born with a genetic disorder, like cystic fibrosis or muscular dystrophy, the father may end up mistakenly believing he carries the gene for that disorder. If that father has siblings, this misinformation could affect their decision to have children. Children, on the other hand, may grow up not knowing they carry a high genetic risk of a particular disease, such as depression, diabetes, or cancer. These days, with the growing role that genetics plays in our health outlook, knowing the identity of your biological father can be as important as knowing your blood type. One day it might save your life.

But most doctors simply don't find such risks to be as compelling as the risk of disrupting the family, which to them would violate the most basic rule of medicine: Do no harm. From day 1 of medical school, this rule is pounded into doctors' heads, and they won't break it easily.

You have to go back to a 1983 report by a presidential commission on ethics in medicine to find anything contradicting the "Don't tell" policy. "At that time, we always thought more information was better," says Lori Andrews, J.D., a professor at Chicago–Kent College of Law and the lead author of a 1994 report for the Institute of Medicine arguing against disclosure. "Since then, I think the whole societal approach to genetic information has changed."

For instance, when scientists created the test for Huntington's disease, an inherited neurological disorder for which there is no cure, it was assumed that everyone would want to know whether or not they were going to develop the condition. "But only about 15 percent of the people at risk had any interest," says Andrews, "because they would rather live with hope than actually know their genetic future." Doctors today, she sug-gests, may have taken a lesson from this and no longer assume that if they stumble across PD, a patient wants to be informed: i.e., "Do no harm."

The available evidence, however, suggests otherwise. Several reports on organ-transplant cases show that some families not only survive the disclosure of PD but often thank doctors for their decision to disclose. "The donor and the recipient were both adamant that we did the right thing in informing them of the result," one group of researchers writes in the Journal of Urology, "and felt that it should always be done."

Even so, there are doctors who counter that disclosing paternity isn't in their job description. "They're not having paternity testing. They're having histological [tissue] testing," says Jeff Punch, M.D., director of the University of Michigan transplant center. "The two are one and the same from a practical standpoint. But from a relationship point of view, patients are paying us for a transplant typing, not for paternity testing."

Patient confidentiality is the second reason physicians cite as the reason they remain silent, with part of the problem being how they define the "patient." With Huntington's, it's pretty clear. Less so with PD.

Doctors determine who's the patient by two criteria: who came to see them, and who is most at risk of immediate harm. If a mother visits a doctor alone, then she's the patient, and it's easier for the doctor to justify disclosing PD only to her than if she showed up with her partner. The second criterion is more complicated. In the past 20 years, says Arthur Caplan, Ph.D., a professor at the Center for Bioethics at the University of Pennsylvania, controversy surrounding reproductive technology has led to the view that the most vulnerable person is the child.

For example, battles over who the "real parent" is when you had a surrogate mother who changed her mind turned on how the outcome would affect the child. And, says Caplan, even fights about how old is too old for in vitro fertilization inevitably boiled down to one question: "Is it really in the best interest of the kid?"

As attention shifted to the well-being of children, they increasingly came to be regarded as the primary patient whenever disclosure entailed some risk of family disruption. But what is this risk?

Kids may be able to accept a nonbiological parent, says Robert Butterworth, Ph.D., a child psychologist in Los Angeles who sees PD cases every year. What they can't accept is finding out that they've been lied to, after a lifetime of hearing that lying is wrong. "Children are very good at pointing out when their parents are hypocrites," Butterworth says. "So the sense of betrayal can lead to anger and disruption. They may withdraw from both parents, the nonbiological as well as the one who lied."

Still, those who oppose disclosure of PD claim that at the very least, the mother will suffer, and that this will indirectly affect the child. "It's a family-values rationale," says Mary Mahowald, Ph.D., a professor emerita at the MacLean Center for Clinical Medical Ethics, in Chicago. "It's likely to break up a marriage if it's disclosed, or the woman might be battered as a result." Such are the arguments, says Mahowald, that have been given over the years. Whether or not that fear is justified, of course, is another story.

"The literature documenting the possibility or probability of a family breaking up or the battering of women is really not good," says Mahowald, "and you could make the argument that if partners are going to separate on grounds of disclosure, maybe they should separate regardless. It might be better for the family. So, to my mind, the family-values rationale is questionable."

It was a cold day in Michigan in Feb-ruary 2002, Shane Shamie remembers. His marriage had fallen apart a few years earlier, and he was still trying to pull his life together. His main concern was his 12-year-old daughter, a tall, awkward child who had become withdrawn after the divorce. When she came over on weekends, they'd hang out and watch a game on TV, or just talk. The idea, says Shamie, was to get her to open up a little. And in time she did--by posing a question Shamie had always somehow managed to avoid asking himself.

"Why does everybody in the family have blue eyes and I have brown eyes?"

Shamie reassured the girl as best he could, struggling to conceal his shock. He and his first wife had been married for 8 years. He'd heard rumors now and then that she'd been stepping out, but he hadn't wanted to believe it. His life back then, after all, had seemed perfect--a high-paying job at a commercial loan company, a beautiful wife, two adoring children. . . . "You don't suspect something like this," Shamie says. "With my family background and her family background, this is just an unaccepted thing."

By the time his daughter started studying genetics in school and thought to ask about her eye color, Shamie had already remarried. His new wife agreed that he should send immediately for a paternity test. It arrived on a Thursday. Two weeks later, the results came back, by e-mail.

"You raise a kid for 12 years and you think it's your kid, and then this news comes. It was heartbreaking," Shamie says. "It was like I had an adoption forced on me. I adopted a child that I didn't even know I adopted."

For all the power they wield in cases of PD, medical doctors aren't the only gatekeepers deciding who should be let in on family secrets. Genetic counselors, master's-level professionals who specialize in advising patients about their risk of genetic disorders, also encounter the tell/don't-tell dilemma.

It's an issue of unusual ethical complexity--and yet, genetic counselors are strangely uniform in their responses. According to a 1992 study in the Journal of Genetic Counseling, nearly 100 percent of 199 counselors felt that the confidentiality of the mother outweighed the presumed father's right to know. These results are all the more dismaying in light of a separate survey showing that 75 percent of patients (mostly women) felt that doctors should tell the dad. Granted, the study of genetic counselors was 15 years ago, but the comments of those practicing today give little reason to believe anything has changed.

Eriskay Burton, M.S., a genetic counselor at the Brooklyn Hospital Center, recalls a case in which testing uncovered an irregularity on a child's Y chromosome, inherited from the father. When subsequent testing revealed that the father was not a carrier of this irregularity, paternal discrepancy was almost certain. "It's our obligation to call him with these results," Burton acknowledges. But, she says, "we're not obligated to suggest to him that it's due to nonpaternity."

This kind of hairsplitting is distressingly common. Another counselor, Suzanne Carter, M.S., of the Albert Einstein College of Medicine, cites scientific uncertainty as her justification for sometimes withholding the truth about a test's implications. "With what the standard is--99.9 percent--can I say that he's been absolutely excluded as the baby's father?" Carter asks. Her answer? "No."

There's a fine ethical line between a sin of omission and a sin of commission. Another genetic counselor, Elsa Reich, M.S., related one case in which a physician explained away a genetic inconsistency by lying to a man, saying that it "was probably a new mutation." When I asked Reich if she would ever resort to this sort of subterfuge herself, she replied, "I've never done that. But might I? I might, I might."

Of course, lying is nothing new in the world of medicine. As late as 1970, doctors infamously withheld cancer diagnoses "for the good of the patient." (After all, they figured, these patients were doomed anyway, so what good would knowing do them?) This ended when it collectively dawned on doctors that, good intentions notwithstanding, paternalism was probably not the best approach. But given the nondisclosure policy of most genetic counselors these days, it might as well be 1970 again--except that now, with women dominating 92 percent of the field, paternalism seems to have been replaced by maternalism.

Patrick Wilson, M.M.Sc., is one of the exceptions to this practice. A search of the National Society of Genetic Counselors' Web site shows that of the 76 genetic counselors specializing in prenatal testing, which is how PD is often exposed, Wilson is one of only three men. So where does he come down on this issue? Does the father have a right to know? "He should know what the results are, and the implications of those results," Wilson says. "If he's under the mistaken assumption that he carries a genetic mutation, he may think that his future children--especially if he has a child with another woman--are at an increased risk of having that particular condition."

Wilson wouldn't go on record as to whether there's a gender bias in his profession, but a comparison from the aforementioned 1992 study suggests that there might be. Of the genetic counselors with M.S. degrees who were surveyed, 93.5 percent were women, while 65 percent of the M.D. and Ph.D. geneticists were men. And how did they come out on disclosure? Some of the geneticists said that they would tell the father if PD was accidentally discovered, but the researchers noted, "Most M.S. counselors chose to tell the mother alone."

In Carnell Smith's view, the only way to solve the PD problem would be to make paternity testing mandatory at birth. Smith, himself a victim of PD, is with the advocacy group U.S. Citizens Against Paternity Fraud. "The child is born and you're being told, 'Look, he's got your eyes, he's got your nose, he's got all your facial features.' That is an emotionally disarming time for any man to be able to make an 18- to 21-year decision, when he doesn't have all the facts."

But Burton doesn't think it's ethical to make such testing compulsory without informed consent from both mother and father. "It would have to be something that they wanted to do," she says. Yet even if both parents were present for the birth and agreed to sign off on testing, she says, there's an even bigger problem: Who's going to pay for it? "Paternity testing can cost up to $400. And medical insurance doesn't cover that. It would be too costly."

Wade Horn, Ph.D., an assistant secretary for children and families at the U.S. Department of Health and Human Services, doesn't see this as being about money. For him, it's about the power of the state. "I'm a father," he says. "I've got two kids, been married 30 years. If somebody had walked in 6 hours after my baby was born in the hospital and said, 'We're going to do genetic testing, open your mouth. . . . ' This is the government forcing you to submit to a genetic test. I'd tell them to go to hell."

More important, he says, mandating genetic testing would deliver the wrong message. "Fatherhood is not simply about shared genetic makeup. It is far more significant than that. And the message that that would send to men all across America, and to our culture, about the meaning of fatherhood would be abhorrent." Besides, he says, in any contested paternity case, federal law requires that the state must provide a paternity test whenever a man requests it.

But in the real world, says Ron Henry, a Washington, D.C.–based lawyer and fathers'-rights activist, it rarely works out that way. "A huge number of these things are resolved by default judgment, or by a guy who just shows up without a lawyer and has no prayer of knowing what's going on. Or you've got a situation where there's social pressure, and the guy is beat up if he asks for a genetic test. You know, 'How dare you challenge me! You were in the hospital when I had this baby, blah blah blah.' So the reality is that surprisingly few people are actually having the test done."

Dylan Davis didn't, and he's regretted it ever since. A 36-year-old Desert Storm vet, Davis now works as a software engineer in Denver. His marriage was already crumbling when a friend of his had the good grace to let him in on a little secret that everyone but him seemed to know: Davis's twins, a boy and a girl, actually belonged to a cook at a seafood restaurant where his wife used to work as a waitress.

"I was completely numb," Davis says. "I felt like such an idiot after all those years, just an absolute fool. Anger hadn't even set in. Depression set in. Because these were not my kids."

Still, Davis didn't claim his right to a paternity test. "I didn't want to raise the issue, for fear of what the judge would say if I came forward and said, 'I don't think those kids are mine.' Yet at the same time, I wanted as much custody of those kids as I could get." The end result: In 2002, Davis was ordered by the court to pay more than $1,000 a month in child support. And 5 years later, he's still paying, even though any relationship he had with the twins has long since disintegrated.

I'm on the phone with Owen Williams (not his real name), who just found out yesterday that the tired child I hear crying in the background, the child he's been rocking to sleep every night, the child who carries his name, belongs to some other man. For a person who's just had his life turned upside down, he seems surprisingly calm.

Williams is a level-headed guy. He's 24 years old and working toward a degree in network engineering. He has clear professional goals. He knows what he wants out of life. And this definitely isn't it.

The child's mother comes home from work in another 6 1/2 hours. She doesn't realize that Williams knows the truth, and he has no plans to tell her. As soon as he finds a new place to live, within a day or two, he hopes, he's going to leave, and that's it. "In fact, when I move out, I'm not saying anything, because there's nothing to be said. For over 15 months, over a year, she deceived me. Every doctor visit I've been to, every cookout I've been to, every reunion I've been to--with her, on her account--I've been deceived."

Yesterday's discovery changed things for Williams. "Knowing that I'm not his father is the part that I'm having trouble with," he explains. "He has nothing to do with what happened between me and her. So I treat him just like any other kid."

The effects of PD on the father-child relationship have never been formally studied, but common sense suggests that the more time a man has to form a bond with the child, the more he'll try to salvage that bond in the aftermath of PD. After raising his daughter for 12 years, Shamie still wants her in his life, but acrimony between him and his ex-wife continues to confound that hope. As for Wise, he later found out that none of his three boys were his. Despite the trauma of this revelation, he still thought of himself as their dad. Today, though, the oldest boy, 18, won't have anything to do with him, and the youngest was 12 when he died of cystic fibrosis in 2004, killed by the disease he inherited from a stranger. "He had to pay the ultimate price," Wise says. "It took his life."

If there's any lesson here for a man, it's this: The medical establishment is not on your side, the legal establishment may or may not be on your side, and you can be damn sure that the woman who lied to you isn't on your side, which makes it all the more important that you stick up for yourself. More important, perhaps, asking a few painful questions in the beginning could save you--and the ones you love--a lot of pain later on. No man can be blamed for believing in the woman he loves. You can't go into love doubting. But nor can you live without truth.

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